Summary of Significant Accounting Policies - Variable Interest Entities (Details) - USD ($) $ in Millions	3 Months Ended
	Jan. 31, 2020	Oct. 31, 2019	Jul. 31, 2019
Variable Interest Entity [Line Items]
Document Period End Date	Jan. 31, 2020
Cash and cash equivalents	$ 1,000	$ 1,370
Variable Interest Entity Primary Beneficiary, Blue Diamond Parts [Member]
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets		32	$ 24
Cash and cash equivalents		2	10
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities		4	3
Variable Interest Entity Primary Beneficiary Securitizations Treated As Borrowings [Member] | Financial Services Operations
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets		927	722
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities		838	648
Transaction Does Not Qualify for Sale Accounting [Member] | Financial Services Operations
Variable Interest Entity [Line Items]
Variable Interest Entity, Consolidated, Carrying Amount, Assets		537	311
Variable Interest Entity, Consolidated, Carrying Amount, Liabilities		$ 279	$ 147